package Test;

import java.util.HashMap;
import java.util.concurrent.CopyOnWriteArrayList;

class A {
    public A(){

    }
}
class B extends A {

}
interface C{
    static void a(){

    }
    abstract void b();
}
public class TestDemo1 {
    public static void main(String[] args) {
        Integer a = 100;
        Double b = 100.0;
        System.out.println(a.doubleValue() == b);
        Object o = new Object();
        String str = new String("  12 3 ");
        System.out.println(str);
        str.trim();
        System.out.println(str);
        CopyOnWriteArrayList<Integer> copyOnWriteArrayList = new CopyOnWriteArrayList<>();
        copyOnWriteArrayList.add(1);
        int size = copyOnWriteArrayList.size();
        System.out.println(size);
        HashMap<String,Integer> hashMap = new HashMap<>();
        hashMap.put("tao",1);
    }
}
